Unexpect fill connection rendering with extreme values

[jonmmease]

Plotlyjs translation of plotly/plotly.py#1008

When creating a rectangle using 4 scatter points (3 line segments) and fill: "toself" the connecting edge of the rectangle behaves oddly when the rectangle is much much larger than the viewport.

CodePen: https://codepen.io/jonmmease/pen/WaapQa

var yval = 1e4
fig = {
  "data": [
    {
      "fill": "toself",
      "type": "scatter",
      "x": [
        1,
        10,
        10,
        1
      ],
      "y": [
        yval,
        yval,
        -yval,
        -yval
      ]
    }
  ],
  "layout": {
    "yaxis": {
      "range": [
        -0.5,
        0.5
      ]
    }
  }
}

Plotly.newPlot('div1', fig);

But it looks as expected with yval is 1e2:

It also work as expected with scattergl traces.

[alexcjohnson]

Thanks @jonmmease - This is happening because we prune away one of those far-offscreen points, since it doesn't affect the visible path. But you're right, to support fills we need to always include the very first and last points.